This invention relates to printers in general and more particularly to a print engine chassis having adjustable side walls to allow mounting motor components on either side of the chassis.
Pre-press color proofing is a procedure used by the printing industry to create representative images of printed material. This procedure avoids the high cost and time required to produce printing plates and set-up a high-speed, high-volume printing press to produce a single intended image for proofing prior to a production run of the intended image. In the absence of pre-press proofing, a production run may require several corrections to the intended image to satisfy customer requirements, and each of the intended images would require a new set of printing plates. By utilizing pre-press color proofing, time and money are saved.
A laser thermal printer having half-tone color proofing capabilities is disclosed in commonly assigned U.S. Pat. No. 5,268,708 titled xe2x80x9cLaser Thermal Printer With An Automatic Material Supply,xe2x80x9d issued Dec. 7, 1993 in the name of R. Jack Harshbarger, et al. The Harshbarger, et al. device is capable of forming an image on a sheet of thermal print media by transferring dye from a roll of dye donor material to the thermal print media. This is achieved by applying thermal energy to the dye donor material to form an image on the thermal print media. This apparatus generally comprises a material supply assembly; a lathe bed scanning subsystem, which includes a lathe bed scanning frame, a translation drive, a translation stage member, a laser printhead, and a rotatable vacuum imaging drum; and exit transports for the thermal print media and dye donor material.
The operation of the Harshbarger, et al. apparatus comprises metering a length of the thermal print media in roll form from a material supply assembly. The thermal print media is measured and cut into sheet form of the required length, transported to the vacuum imaging drum, registered, and wrapped around and secured to the vacuum imaging drum. A length of dye donor roll material is metered out of the material supply assembly, measured, and cut into sheets of the required length. The cut sheet of dye donor roll material is then transported to and wrapped around the vacuum imaging drum, and superposed in registration with the thermal print media. The scanning subsystem traverses the printhead axially along the rotating vacuum imaging drum in to produce the image on the thermal print media. The image is written in a single swath, traced out in the pattern of a continuous spiral, concentric with the imaging drum, as the printhead is moved in parallel to the drum axis.
Although the printer disclosed in the Harshbarger, et al. patent performs well, there is a long-felt need to reduce manufacturing costs for this type of printer and for similar types of imaging apparatus. With respect to the lathe bed scanning frame disclosed in the Harshbarger, et al. patent, the machined casting used as the frame represents significant cost relative to the overall cost of the printer. Cost factors include the design and fabrication of the molds, the casting operation, and subsequent machining needed in order to achieve the precision necessary for a lathe bed scanning engine used in a printer of this type. Castings present inherent problems in modeling, making it difficult to use tools such as finite element analysis to predict the suitability of a design. Moreover, due to shrinkage, porosity, and other manufacturing anomalies, it is difficult to obtain uniform results when casting multiple frames. In the assembly operation, each frame casting must be individually assessed for its suitability to manufacturing standards and must be individually machined. Further, castings also exhibit frequency response behavior, such as to resonant frequencies, which are difficult to analyze or predict. For this reason, the task of identifying and reducing vibration effects can require considerable work and experimentation. Additionally, the overall amount of time required between completion of a design and delivery of a prototype casting can be several weeks or months.
Alternative methods used for frame fabrication have been tried, with some success. For example, welded frame structures have been used. However, these welded structures require skilled welding and significant expense in manufacture. Whether using a casting or weldment, the design of the print engine is optimized for imaging with the printhead moving either from left to right along the leadscrew or from right to left. Drive motors are appropriately positioned on one side of the print engine frame or the other. The side walls of the print engine frame that provides support for these drive motors have dimensions which this support function. The side wall of the print engine frame that does not support motor mounts is correspondingly less massive than the opposite side wall.
It would be useful to provide a print engine chassis design that, with only minor variations in assembly practices, allows the writing direction for a printer to be reversed, without requiring redesign of the drive system, translation assembly, and lead screw.
An object of the present invention is to provide a sheet metal structure for a print engine chassis that can be configured for either a left-to-right or a right-to-left imaging path.
According to one aspect of the present invention, a print engine chassis for supporting an imaging drum, an imaging drum motor, and a printhead translation assembly, and translation motor, comprises a sheet metal frame comprised of a plurality of interlocking rigid members. The interlocking rigid members form a first and a second side wall disposed on opposite ends of the imaging drum. A thickness of the first sidewall is adjustable and a thickness of the second side walls is adjustable to allow the thickness of each sidewall to be varied to accommodate either a right-to-left or a left-to-right imaging direction.
According to an embodiment of the present invention, sheet metal pieces are cut to form interlocking rigid members, which have tabs and slots that allow the interlocking rigid members to be quickly assembled by hand in order to form the sheet of the chassis. Alternate tabs and slots are provided to permit multiple configurations of side-wall thickness.
A feature of the present invention is a method of manufacturing a chassis that can be easily assembled, but is at the same time structurally rigid and a suitable replacement for a metal casting or weldment.
An advantage of the present invention is that individual interlocking rigid members can be modified in order to change the design of the chassis, and modify the size or configuration of the overall structure. This contrasts with methods using a casting, which cannot be easily modified or scaled dimensionally.
Another advantage of the present invention is cost savings, since a small number of parts serves multiple printer configurations. The present invention allows the same print engine chassis design to be used, with minor variations in assembly methods, to accommodate a printhead assembly that writes either from right to left, or from left to right along a lead screw translation system. The present invention provides a chassis that is structurally rigid, economical, and can be easily modified.
These and other objects, features, and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings, wherein there is shown and described illustrative embodiments of the invention.
The invention and its objects and advantages will become more apparent in the detailed description of the preferred embodiment presented below.